Nice, but she looks out of proportion. Her spine looks too long and her bum too low for the way you have her positioned. It looks like you drew her with her as if she were sticking out her tush, but the crack of her bum is so low that it looks more like she were sitting normal. So I'm guessing that you took some "artistic license" and put her in more flirty position and elongated her back, but the model in real life was sitting in a more natural position. You might want to fix her bum a bit so she's in either the arse-flaunting position or true to life, but it can't be both because it looks unnatural.